1. Field of the Invention
The invention relates to transformers for use in static inverters. Static inverters are devices in which electrical energy in the dc form is converted to electrical energy in the ac form through static means. The present invention lies in the class of inverters in which the dc source produces a current through one or two semiconductor devices, each connected in series with a primary winding of a power transformer and producing an ac output in a transformer secondary winding as the semiconductor devices are switched. The transformers as described herein are adapted for use in inverters using one or two transistor configurations, and include control windings, which are coupled to an input electrode of the semiconductor device to effect efficient and stress free switching.
2. Description of the Prior Art
Static inverters of the class employing a dc source, one or two switching semiconductor devices and a transformer are well known. The arrangements may exist in either free running or the driven form. Representative static inverters are illustrated in U.S. application Ser. No. 956,578 of Hesler et al, now U.S. Pat. No. 4,202,031, assigned to the assignee of the present invention. In either free running or driven form, feedback windings may be used to effect switching of the semiconductor devices. Recently, as represented by U.S. Pat. No. 3,914,680 and U.S. Pat. No. 4,002,999 to Hesler et al and assigned to the Assignee of the present invention, the transformer properties have been tailored to the requirements of the semiconductor in the inverter application, in particular to maximise the switching efficiency and to avoid unduly stressing the semiconductor devices resulting from full core saturation. In both cited patents, the main core is provided with an aperture (or two, in the two transistor inverters), each of which divides the core into two localized branches. One branch is designed to saturate first, and upon saturation to reduce the regenerative and increase the degenerative feedback applied to the transistor, so as to prevent full core saturation. The patented circuits have led to a reduction in cost of such inverters, and a substantial improvement in the switching efficiencies. The present invention represents a further improvement of such arrangements.